1. Technical Field
The present invention relates generally to the art of concrete construction. More particularly, the present invention relates to an apparatus for facilitating the placement of slip dowel rods within adjacent concrete slabs.
2. Related Art
In the concrete construction arts, “cold joints” between two or more poured concrete slabs are frequently used for the paving of sidewalks, driveways, roads, and flooring in buildings. Such cold joints frequently become uneven or buckled due to normal thermal expansion and contraction of the concrete and/or compaction of the aggregate caused by inadequate preparation prior to pouring of concrete. As a means of preventing bucking or angular displacement of such cold joints, it is common practice to insert smooth steel dowel rods generally known as “slip dowels” within the edge portions of adjoining concrete slabs in such a matter that the concrete slabs may slide freely along one or more of the slip dowels, permitting linear expansion and contraction of the slabs while also maintaining the slabs in a common plane and thus preventing undesirable bucking or unevenness of the cold joint.
In order to function effectively, slip dowels must be accurately positioned parallel within the adjoining concrete slabs. The non-parallel positioning of the dowels will prevent the desired slippage of the dowels and will defeat the purpose of the “slip dowel” application. Additionally, the individual dowels must be placed within one or both of the slabs in such a manner as to permit continual slippage or movement of the dowels within the cured concrete slab(s).
A number of methods of installing smooth slip dowels are popular. According to one method, a first concrete pour is made within a pre-existing form. After the first pour has cured, and edge of the form, usually a wooden stud, is stripped away. A series of holes are then drilled parallel into the first pour along the exposed edge from which the form has been removed. The depth and diameter of the individual holes varies depending on the application and the relative size of the concrete slabs to be supported. As a general rule, however, such holes are at least twelve inches deep and typically have a diameter of approximately five-eighths (⅝) of an inch.
After the parallel series of holes have been drilled into the first pour, smooth dowel rods are advanced into each hole such that one end of each dowel rod is positioned within the first pour and the remainder of each dowel rod is positioned within the first pour and the remainder of each dowel rod extends into an adjacent area where a second slab of concrete is to be poured. Thereafter, concrete is poured into such adjacent area and is permitted to set with the parallel aligned dowels extending thereto. After the second pour has cured, the slip dowels will be held firmly within the second slab, but will be permitted to slide longitudinally within the drilled holes of the first slab thereby accommodating longitudinal expansion and contraction of the two slabs while at the same time preventing buckling or angular movement therebetween.
Although the above-described “drilling method” of placing slip dowels is popular, it will be appreciated that such method is extremely labor intensive. In fact, it takes approximately ten minutes to drill a five eighths inch (⅝″) diameter by twelve inch long hole into the first pour and the drilling equipment, bits, accessories, and associated set up time tends to be very expensive. Moreover, the laborers who drill the holes and place the slip dowels must be adequately trained to ensure that the dowels are arranged perpendicular to the joint but parallel to one another so as to permit the desired slippage.
Another popular method of placing slip dowels involves the use of wax-treated cardboard sleeves positioned over one end of each individual dowel. According to such method, a series of holes are drilled through one edge of the concrete form and smooth dowels are advanced through each such hole. Thereafter, the treated cardboard sleeves are placed over one end of each dowel, with a first pour subsequently being made within the form which covers the ends of the dowels including the cardboard sleeves thereon. After the first pour has set, the previously drilled form is stripped away, leaving the individual dowels extending into a neighboring open space where the second pour is to be made. Subsequently, the second pour is made and cured. Thereafter, the slip dowels will be firmly held by the concrete of the second pour, but will be permitted to longitudinally slide against the inner surfaces of the wax treated cardboard sleeves within the first pour. Thus, the waxed cardboard sleeves facilitate longitudinal slippage of the dowels, while at the same time holding the two concrete slabs in a common plane, and preventing undesirable buckling or angular movement thereof.
This method was also associated with numerous deficiencies, namely, that after the first pour was made, the free ends of the dowels were likely to project as much as eighteen inches through the form and into the open space allowed for the second pour. Because the drilled section of the form must be advanced over those exposed sections of dowel to accomplish stripping or removal of the form, it is not infrequent for the exposed portions of the dowels to become bent and, thus, non-parallel. Additionally, the drilled section of the form became damaged or broken during the removal process, thereby precluding its reuse.
Each of the above described known methods of placing slip dowels between concrete slabs often results in the dowels being finally positioned at various angles rather than in the desired parallel array. Therefore, the necessary slippage of the dowels is impeded or prevented.
In response to such deficiencies in the art, a number of dowel placement sleeves have been developed. One such development is U.S. Pat. No. 5,005,331 to Shaw, et al., which is wholly incorporated by reference herein, teaches a slip dowel positioning device that is extractable from the first concrete slab. The device is comprised of a hollow cylindrical portion with a flange or gusset extending perpendicularly therefrom. The flange permitted the device to be attached to the form, and upon curing, the form was removed, thereby also removing the positioning device. Thereafter, a smooth dowel was inserted in the cavity formed in the space previously occupied by the positioning device, and a subsequent slab of concrete was poured. One of the deficiencies associated with the '331 device was that it was required to be removed from a cured slab of concrete, necessitating extra force during removal. Further, the configuration which enabled the positioning device to be removable resulted in a cavity which was less than ideal, in that slight discrepancies in the angular displacement of the smooth dowel are introduced. Therefore, slip dowel placement which was truly parallel to the concrete surface is not possible.
Thus, alternatively, the '331 patent and additionally U.S. Pat. No. 5,216,862 to Shaw, et al., which is also incorporated by reference wherein, contemplated a positioning device which remained in the concrete slab. The positioning device was attached to the form via staples or small nail heads, and forcibly stripped upon curing of the first slab of concrete. However, the requirement of forcibly removing the form from the positioning device remained.
Accordingly there is a need in the art for an inexpensive and readily reproducible dowel positioning device which can remain in the concrete slab after curing. Further, there is a need for a dowel positioning device which can be attached and removed from a form with minimal force and a minimum number of extraneous components. These needs and more are accomplished with the present novel and inventive device, the details of which are discussed more fully hereunder.